A major Australian study finds that a child's long-term weight is closely tied to their parents' BMI before birth, especially the mother's, underscoring the urgent need to tackle obesity before pregnancy to break the cycle across generations.
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New research being presented at this year's European Congress on Obesity (ECO 2025) highlights the need to support women and their families with overweight or obesity to optimise their health and weight before they become pregnant.
The Australian study found that the greater a woman's BMI in pregnancy, the greater her child's weight from birth to age ten. This was the case regardless of whether the woman took part in a dietary and lifestyle intervention (LI) while pregnant or received standard antenatal care (SC). They also reported that the BMI of the father significantly influences the child's weight at age 10.
The results are the latest from the LIMIT trial, which involved 2121 pregnant women with overweight or obesity (average age 29.4 years, median BMI 31.1 in early pregnancy).
Half of the women took part in the LI, which consisted of advice and support for eating a healthy diet (for example, eating more fruit and fibre and reducing intake of refined carbohydrates and saturated fat) and increasing physical activity. The other participants received standard antenatal care (standard care group, SC).
"Women with overweight or obesity are at increased risk of pregnancy complications, like gestational diabetes, high blood pressure, caesarean birth and high infant birth weight, and for their children to develop obesity," says researcher Professor Jodie Dodd, of the University of Adelaide, South Australia, Australia.
"With approximately 50% of women entering pregnancy with overweight or obesity, the trial was carried out to see if changes in diet and physical activity during pregnancy could reduce these risks."
The initial results1, published in 2014, showed that infants whose mothers participated in the LI group were 18% less likely to have birth weights above 4kg (8lb 13oz), a known risk for childhood obesity. However, the two groups had no other differences in maternal or birth outcomes, including pregnancy complications.
The children were also followed throughout childhood. There was no evidence of a difference in the health or growth of the children from women in either the LI or SC group.
For the latest study, Professor Dodd and colleagues examined the effect of maternal BMI in early pregnancy on childhood weight and other measures of growth taken at birth and aged 6 months, 18 months, 3-5 years old, and 8-10 years old.
They found that a child's growth was linked to its mother's BMI in early pregnancy – and that every 5kg/m2 increase in a woman's BMI was associated with an increase in their child's BMI by 0.11kg/m2 at birth, to 0.74kg/m2 at 8-10 years of age.
The effect of maternal BMI became more prominent at age 3-5 and was particularly noticeable at 8-10. This was the case across the different measures of child growth studied—BMI, weight, and their standardised measures. Additionally, paternal BMI impacted child weight and BMI, particularly at ages 8-10.
Professor Dodd says: "We know that women living with overweight or obesity are at increased risk of complications like high blood pressure in pregnancy. We also know that lifestyle interventions during pregnancy are ineffective for improving health outcomes for women and their baby/child.(1, 2, 3)
"What we found here was that a woman's BMI in early pregnancy impacts how her child grows from birth to 8-10 years of age –so, if a woman's BMI is higher going into pregnancy, her child's risk of overweight and obesity increases too. Fathers also have a role to play, as paternal BMI also contributes to child obesity.
"It's vital that healthcare providers focus on supporting women and their families to optimise their health and weight before pregnancy, if we are to intervene and potentially reduce the intergenerational cycle of obesity."